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Processing Incoming Packets
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<p>

Smack provides a flexible framework for processing incoming packets using two constructs:
<ul>
	<li><tt>org.jivesoftware.smack.PacketCollector</tt> -- a class that lets you 
		synchronously wait for new packets.
	<li><tt>org.jivesoftware.smack.PacketListener</tt> -- an interface for asynchronously 
		notifying you of incoming packets. 
</ul>	
A packet listener is used for event style programming, while a packet collector has a 
result queue of packets that you can do polling and blocking operations on. So, a packet 
listener is useful when you want to take some action whenever a packet happens to come in, 
while a packet collector is useful when you want to wait for a specific packet to 
arrive. Packet collectors and listeners can be created using an <tt>XMPPConnection</tt> instance.<p>
	
The <tt>org.jivesoftware.smack.filter.PacketFilter</tt> interface determines which
specific packets will be delivered to a <tt>PacketCollector</tt> or <tt>PacketListener</tt>.
Many pre-defined filters can be found in the <tt>org.jivesoftware.smack.filter</tt> package.

<p>
The following code snippet demonstrates registering both a packet collector and a packet
listener:<p> 
 
<div class="code"><pre>
<font color="gray"><i>// Create a packet filter to listen for new messages from a particular</i></font>
<font color="gray"><i>// user. We use an AndFilter to combine two other filters.</i></font>
PacketFilter filter = new AndFilter(new PacketTypeFilter(<b>Message.class</b>), 
        new FromContainsFilter(<font color="green">"mary@jivesoftware.com"</font>));
<font color="gray"><i>// Assume we've created a XMPPConnection name "connection".</i></font>

<font color="gray"><i>// First, register a packet collector using the filter we created.</i></font>
PacketCollector myCollector = connection.createPacketCollector(filter);
<font color="gray"><i>// Normally, you'd do something with the collector, like wait for new packets.</i></font>

<font color="gray"><i>// Next, create a packet listener. We use an anonymous inner class for brevity.</i></font>
PacketListener myListener = new PacketListener() {
        <b>public</b> <b>void</b> processPacket(Packet packet) {
            <font color="gray"><i>// Do something with the incoming packet here.</i></font>
        }
    };
<font color="gray"><i>// Register the listener.</i></font>
connection.addPacketListener(myListener, filter);
</pre></div><p>

<p class="subheader">
Standard Packet Filters
</p>

A rich set of packet filters are included with Smack, or you can create your own filters by coding
to the <tt>PacketFilter</tt> interface. The default set of filters includes:
<ul>
	<li> <tt>PacketTypeFilter</tt> -- filters for packets that are a particular Class type.
	<li> <tt>PacketIDFilter</tt> -- filters for packets with a particular packet ID.
	<li> <tt>ThreadFilter</tt> -- filters for message packets with a particular thread ID.
	<li> <tt>ToContainsFilter</tt> -- filters for packets that are sent to a particular address.
	<li> <tt>FromContainsFilter</tt> -- filters for packets that are sent to a particular address.
	<li> <tt>PacketExtensionFilter</tt> -- filters for packets that have a particular packet extension.
	<li> <tt>AndFilter</tt> -- implements the logical AND operation over two filters.
	<li> <tt>OrFilter</tt> -- implements the logical OR operation over two filters.
	<li> <tt>NotFilter</tt> -- implements the logical NOT operation on a filter.
</ul>



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